The discovery that every-day, ‘normal temperature’, biological systems – plants – use quantum effects in the process of photosynthesis has been advancing for several years. For physicists and biologists this is becoming something of a revelation. Physicists in particular, accustomed to observing quantum effects only at extreme cold (approaching absolute zero), find the idea that Nature has adapted quantum effects to the warm and chaotic environment of living things almost shocking. Yet the evidence is mounting. In 2007 researchers led by Greg Engel at the University of Berkeley California (USA) and Graham Fleming at the Lawrence Berkeley National Laboratory (USA) demonstrated that quantum coherence existed in the so called antenna proteins (sunlight receptors) in green sulfur bacteria. In late 2009, researchers led by Greg Scholes at the University of Toronto (Canada) used laser pulses to set protein molecules spinning, and observed that the energy patterns fluctuated in a way that showed there were connections between them – connections called quantum entanglement. [SciTechStory: Quantum mechanics in photosynthesis, oh my]

Now a new collaborative team, including Graham Fleming, has added confirmation that the photosynthetic process uses quantum entanglement to utilize nearly 100% of the sun’s energy in the conversion of sunlight to carbon-based (sugar) energy.

The new study published in the journal Nature Physics in May, provides confirmation of quantum effects in a specific photosynthetic mechanism, and according to Mohan Sarovar, one of the authors:

“…this is the first instance in which entanglement has been examined and quantified in a real biological system.” … “We present strong evidence for quantum entanglement in noisy non-equilibrium systems at high temperatures by determining the timescales and temperatures for which entanglement is observable in a protein structure that is central to photosynthesis in certain bacteria.”

Quantum entanglement is one of the signature effects in the strange-seeming world of quantum physics. It basically involves two atomic particles, which though physically separated, behave as if they were one particle; they are ‘entangled.’ The new study establishes that various pigments in a specific light harvesting protein (called, technically, the Fenna-Matthews-Olson or FMO protein) use quantum entanglement to simultaneously choose the optimum pathway for capturing photons of light – capturing all of them. Such efficiency human engineers can only dream about.

Having demonstrated entanglement in the FMO protein, the researchers believe the same effect will also be found in larger light harvesting proteins and, in fact, there may be multiple instances of the effect to act like a kind of highly adaptive filter, trapping the photons of light as they penetrate into the pigments of the protein.

The researchers remain surprised at much of what they discovered: That the entanglement effect persisted even when the molecules of the protein were not strongly coupled (connected) with electronic and vibrational states, and that temperature has so little impact on the process. It appears that the light harvesting quantum effects in plants are almost immune to heat – especially in comparison to quantum effects that are produced in the laboratory.

It should be emphasized that this is pioneer work. Only a few years ago, most scientists did not consider the possibility that natural processes might use quantum effects. Now we are nearly sure that quantum effects lie at the heart of one of the most important natural processes of all. Photosynthesis is the basis of most life as we know it (including our own, since we must eat energy produced by photosynthesis). Eventually, some of the knowledge gained in this area will contribute to human-made artificial photosynthesis. It may also be a path that leads to other fundamental discoveries about the nature of quantum physics, which are now almost totally unsuspected. Great stuff for both biologists and physicists.